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Immediately WAL-log subtransaction and top-level XID association.

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The logical decoding infrastructure needs to know which top-level
transaction the subxact belongs to, in order to decode all the
changes. Until now that might be delayed until commit, due to the
caching (GPROC_MAX_CACHED_SUBXIDS), preventing features requiring
incremental decoding.

So we also write the assignment info into WAL immediately, as part
of the next WAL record (to minimize overhead) only when wal_level=logical.
We can not remove the existing XLOG_XACT_ASSIGNMENT WAL as that is
required for avoiding overflow in the hot standby snapshot.

Bump XLOG_PAGE_MAGIC, since this introduces XLR_BLOCK_ID_TOPLEVEL_XID.

Author: Tomas Vondra, Dilip Kumar, Amit Kapila
Reviewed-by: Amit Kapila
Tested-by: Neha Sharma and Mahendra Singh Thalor
Discussion: https://postgr.es/m/688b0b7f-2f6c-d827-c27b-216a8e3ea700@2ndquadrant.com
This commit is contained in:
Amit Kapila
2020-07-20 08:48:26 +05:30
parent d05b172a76
commit 0bead9af48
9 changed files with 108 additions and 24 deletions
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3
src/include/access/xact.h
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@@ -428,6 +428,9 @@ extern void UnregisterXactCallback(XactCallback callback, void *arg);
extern void RegisterSubXactCallback(SubXactCallback callback, void *arg);
extern void UnregisterSubXactCallback(SubXactCallback callback, void *arg);
extern bool IsSubTransactionAssignmentPending(void);
extern void MarkSubTransactionAssigned(void);
extern int xactGetCommittedChildren(TransactionId **ptr);
extern XLogRecPtr XactLogCommitRecord(TimestampTz commit_time,

1
src/include/access/xlog.h
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@@ -237,6 +237,7 @@ extern bool XLOG_DEBUG;
*/
#define XLOG_INCLUDE_ORIGIN 0x01 /* include the replication origin */
#define XLOG_MARK_UNIMPORTANT 0x02 /* record not important for durability */
#define XLOG_INCLUDE_XID 0x04 /* include XID of top-level xact */
/* Checkpoint statistics */

2
src/include/access/xlog_internal.h
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@@ -31,7 +31,7 @@
/*
* Each page of XLOG file has a header like this:
*/
#define XLOG_PAGE_MAGIC 0xD106 /* can be used as WAL version indicator */
#define XLOG_PAGE_MAGIC 0xD107 /* can be used as WAL version indicator */
typedef struct XLogPageHeaderData
{

3
src/include/access/xlogreader.h
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@@ -191,6 +191,8 @@ struct XLogReaderState
RepOriginId record_origin;
TransactionId toplevel_xid; /* XID of top-level transaction */
/* information about blocks referenced by the record. */
DecodedBkpBlock blocks[XLR_MAX_BLOCK_ID + 1];
@@ -304,6 +306,7 @@ extern bool DecodeXLogRecord(XLogReaderState *state, XLogRecord *record,
#define XLogRecGetRmid(decoder) ((decoder)->decoded_record->xl_rmid)
#define XLogRecGetXid(decoder) ((decoder)->decoded_record->xl_xid)
#define XLogRecGetOrigin(decoder) ((decoder)->record_origin)
#define XLogRecGetTopXid(decoder) ((decoder)->toplevel_xid)
#define XLogRecGetData(decoder) ((decoder)->main_data)
#define XLogRecGetDataLen(decoder) ((decoder)->main_data_len)
#define XLogRecHasAnyBlockRefs(decoder) ((decoder)->max_block_id >= 0)

1
src/include/access/xlogrecord.h
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@@ -223,5 +223,6 @@ typedef struct XLogRecordDataHeaderLong
#define XLR_BLOCK_ID_DATA_SHORT 255
#define XLR_BLOCK_ID_DATA_LONG 254
#define XLR_BLOCK_ID_ORIGIN 253
#define XLR_BLOCK_ID_TOPLEVEL_XID 252
#endif /* XLOGRECORD_H */